chp 16 homework questions
When an air molecule is hit by an approaching, faster moving molecule, does the approaching molecule's rebound speed increase or decrease? How about when it hits a receding molecule?
Increase, decrease
Does a good insulator prevent heat from escaping or slow its passage?
Insulators slow the passage of heat.
Why does the pupil of the eye appear black?
Light that enters the pupil bounces several times before exiting, and is absorbed on each bounce, so little light exits.
What would be the consequence of completely eliminating the greenhouse effect?
The average temperature on the surface of Earth would drop to -18°C.
How much radiant energy from the Sun, on average, reaches each square meter at the top of Earth's atmosphere each second? What is the average solar power, averaged over a whole year, which reaches the United States?
1.4 kJ, 0.18 kW/m2
In what form does radiant energy travel?
As electromagnetic waves
Which will normally warm faster: a black pot of cold water or a silvered pot of cold water? Which will cool faster?
Black, black
Distinguish between weather and climate.
Climate is what you expect, whereas weather is what you get.
What is the role of "loose" electrons in heat conductors?
Free electrons can move through a material carrying heat, jostling atoms and other electrons.
How does glass act like a one-way valve for a conventional greenhouse? Does the atmosphere similarly act as a one-way valve?
Glass transmits solar radiation into the greenhouse and blocks infrared radiation from leaving the greenhouse. The same thing happens in the atmosphere.
What happens to the temperature of something that radiates energy without absorbing the same amount in return?
It cools.
What determines whether an object is a net absorber or a net emitter of radiant energy at a given time?
It is determined by the temperature of the object relative to its surroundings. Hotter objects are net emitters.
If you touch the metal sides in an oven with your bare hand, you're in trouble. But hold your hand briefly in the oven air and you're okay. What does this tell you about the relative conductivities of metal and air?
Metal is a good conductor of heat, whereas air is a terrible conductor of heat
Can an object be both a good absorber and a good reflector at the same time?
No. A good absorber reflects very little light.
Since all objects emit energy to their surroundings, why don't the temperatures of all objects continuously decrease?
Objects that are good emitters are equally good absorbers, so they absorb radiation as well as emit it.
Why are materials such as wood, fur, feathers, and even snow good insulators?
Outer electrons in these materials are firmly attached.
An object that radiates energy at night is in contact with the relatively warm Earth. How does poor conductivity affect the object's temperature relative to the air temperature?
Poor thermal conductivity causes it to get colder with respect to the air than good thermal conductivity does.
Explain why a firewalker can step quickly without harm on red-hot coals with bare feet.
Wood, even as glowing coals, is a poor conductor of heat.
Relatively speaking, do high-frequency waves have long wavelengths or short wavelengths? Name an electromagnetic wave with higher frequency than blue light.
Short, ultraviolet
Cite a primary difference between waves of solar radiation and waves of terrestrial radiation.
Solar radiation peaks at shorter wavelengths in the visible, whereas terrestrial radiation peaks at longer wavelengths in the infrared.
How are the speeds of molecules of air affected as they separate from one another when escaping from the nozzle of a party balloon? What happens to the temperature of the air?
Speeds decrease; temperature decreases.
How are the speeds of molecules of air affected when the air is compressed by the action of a tire pump? What happens to the temperature of the air?
Speeds increase; temperature increases.
What is terrestrial radiation?
Terrestrial radiation is infrared radiation emitted by Earth's surface.
What does a windchill of -20°C mean?
The cooling rate will be the same as if the temperature were -20°C without wind.
Why isn't Millie's hand burned when she holds it above the escape valve of the pressure cooker (see Figure 16.8 in the textbook)?
The escaping gas is cooled by expansion.
How does the peak frequency of radiant energy relate to the absolute temperature of the radiating source?
The peak frequency increases as temperature increases.
Which will undergo the greater rate of cooling: a red-hot poker in a warm oven or a red-hot poker in a cold room (or do both cool at the same rate)?
The poker in the cold room cools fastest.
Why does the direction of coastal winds change from day to night?
The specific heat of water is greater than the specific heat of land. Water cools more slowly at night. The temperature difference drives convection and offshore winds.
Cite three ways in which a Thermos bottle inhibits heat transfer.
There is no conduction and no convection through a vacuum, and silvered surfaces stops radiation.
What happens to the volume of air as it rises? What happens to its temperature?
Volume increases; temperature decreases.
